JP2010243495A - Device for optically inspecting surface of matter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a device and method for automatically and rapidly performing the optical inspection of the surface of matter with good reliability and high precision. <P>SOLUTION: The device (10) for optically inspecting the surface (58) of the matter (56) has: a pattern (28) having many bright and dark regions (29 and 30) forming spatial first intensity distributions (31) having a spacial first cycle; a housing part (54) for positioning the matter having a surface with respect to the pattern so that the first intensity distributions may be applied to the surface of the matter; a control unit (20) displacing the first intensity distributions with respect to the surface (58) by a predetermined displacement distance so that the surface may take a large number of positions different with respect to the first intensity distributions along the displacement distance; an imaging unit (50) photographing a large number of images showing the surface of the matter at different positions along with the first intensity distributions; and an evaluation unit (46) determining surface characteristics in relation to the images. A measuring instrument (48) determines the present position of the first intensity distribution with respect to the matter. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

The present invention relates to an apparatus for optically inspecting the surface of an object.
A pattern having a number of bright and dark areas forming a spatial first intensity distribution having a first spatial period;
An accommodating portion for positioning an object having a surface relative to the pattern so that the first intensity distribution is on the surface;
A control unit for displacing the first intensity distribution by a predetermined displacement distance relative to the surface so that the surface assumes a number of different positions relative to the first intensity distribution along the displacement distance. When,
At least one imaging unit for capturing a number of images according to the image at different positions along with the first intensity distribution;
And an evaluation unit for determining the properties of the surface in relation to the image.

Furthermore, the present invention is a method for optically inspecting the surface of an object,
Providing a pattern having a number of bright and dark regions forming a spatial first intensity distribution having a spatial first period;
Positioning the object having a surface relative to the pattern such that the first intensity distribution is on the surface;
The first intensity distribution is displaced by a predetermined displacement distance relative to the surface so that the surface takes a number of different positions relative to the first intensity distribution along the displacement distance. And steps to
Photographing a number of images showing the surface at different positions together with the first intensity distribution;
Determining the characteristics of the surface in relation to an image.

  Such an apparatus and such a method are known, for example, from WO 2009/007130 (Patent Document 1).

  In the case of industrial production of products, the quality of products has become increasingly important in recent years. On the one hand, high quality can be achieved by the designed and stable production process. On the other hand, it is necessary to control the quality parameters of the product completely and reliably as much as possible to detect quality defects early. In many cases, surface quality is an important part of product characteristics. In this case, the surface to be decorated, such as a painted surface in an automobile, or a technical surface, such as the surface or bearing of a micromachined metal piston, is a problem.

  A number of proposals and concepts already exist for automatically inspecting such surfaces. The deflection measurement method is a concept that is highly promising for at least partially reflecting surfaces, and observes a pattern with bright and dark areas over the inspection surface. The pattern is displaced relative to the surface. It is possible to optically inspect the reflective surface based on the changes that the observation area undergoes due to reflection. For example, the local slope of the surface location can be measured from at least three images with different relative positions of the pattern. Based on the local slope, scratches, protrusions, recesses, holes and other dimensional defects can then be detected. Surface brightness and scattering properties can be determined by deflection measurements.

  Patent Document 1 mentioned at the beginning describes an apparatus and method for optically inspecting an at least partially reflective surface of an object, in which case the surface is inspected by a deflection measurement method. The entire detailed description of deflection measurement evaluation disclosed in Patent Document 1 is incorporated herein by reference. A known device has a tunnel, and a stripe pattern is provided on the inner wall of the tunnel, and the stripe pattern forms a sinusoidal intensity distribution. An object having an inspection surface, in this case an automobile, is passed through the tunnel. In the meantime, the surface to be inspected is photographed by a plurality of cameras. Due to the relative movement of the surface relative to the pattern, the intensity distribution moves from the camera field of view to the surface. When this method is implemented, it is advantageous to image each inspection surface location at at least four different positions relative to the pattern, where at least four different positions represent exactly one period of the intensity distribution. cover. According to Patent Document 1, this can be achieved by accurately matching the moving speed of the automobile in the tunnel to the geometric ratio of the pattern in the tunnel.

International Publication No. 2009/007130 Pamphlet

  The object of the present invention against the background of such technology is to propose an alternative apparatus and method for inspecting a surface in a wide range automatically, quickly, reliably and with high accuracy. . In this case, it is desirable that the apparatus and method can be used universally and can be implemented at low cost.

  This object is achieved according to one aspect of the invention by an apparatus of the type mentioned at the outset having a measuring device configured to determine the current position of the first intensity distribution relative to the object. Solved.

  According to another aspect of the invention, this problem is solved by a method for determining the current position of the first intensity distribution relative to the object in the method listed at the outset.

  The new apparatus and the new method determine the current position of the intensity distribution relative to the surface by means of a suitably configured measuring unit. In other words, the relative position of the intensity distribution relative to the surface is determined for a number of different current positions based on measurements related to the individual states. Preferably, also in the new apparatus and the new method, the surface is inspected in a deflection measurement manner, so that the current position is not required for surface inspection, unlike in the case of, for example, trigonometric evaluation. However, the current position related to the actual situation is prepared as additional information, and in particular, imaging is simplified. The current position is not required as a parameter for evaluating the deflection measurement formula. However, it is desirable to take images at as uniform intervals as possible. The sum of the intervals corresponds to the period of the intensity distribution. This can be ensured by the measuring unit more easily and cheaply than with the prior art. Furthermore, the new apparatus and the new method can be easily adapted to changes in use and operating conditions. This allows the new device and the new method to be used more flexibly than the known device and the known method.

  The surface position can be used very particularly advantageously to compensate for synchronization variations when the pattern is displaced relative to the surface. Thereby, the new device and the new method allow an inexpensive implementation since relative displacement can be performed by a simpler drive device, despite the fact that an additional measuring unit is provided. In a particularly advantageous embodiment, the pattern is a predefined invariant (passive) pattern, for example printed on a thin film or another pattern carrier, in which case the support is mechanically moved relative to the surface. To do. Furthermore, passive patterns drawn on or etched into the support are also conceivable.

  As described in Patent Document 1, the displacement of the pattern relative to the surface can be performed by moving the object. However, it is also particularly advantageous to displace the pattern by moving the pattern carrier. In this case, the inspection surface is preferably stationary or can be moved in a similar manner in addition to the movement of the object. In deflection measurement inspection, the relative movement between the pattern and the surface is important. The movement can be a linear movement or a rotational movement in any case. Linear movement can be performed very inexpensively, especially for large objects, using a conveyor belt that moves the object along a stationary pattern in the tunnel. By detecting the current position, it is possible to take into account the synchronous fluctuation of the conveyor belt at the time of image capture (image capture time) and evaluation. The rotational movement can be carried out very advantageously by means of a pattern carrier that rotates about the object, for example a cylindrical tunnel that rotates about the longitudinal axis. Advantageously, a circular tube provided with a pattern on the inner peripheral surface can serve as a pattern carrier. By detecting the current position, it is also possible to take into account the synchronous fluctuation of the rotary carrier at the start of imaging and image evaluation.

  In order to detect the current position, it is advantageous to use at least one sensor placed stationary with respect to the object having the surface. However, it is also possible to place the sensor stationary with respect to the pattern so that the sensor detects the current position of the surface relative to the pattern having an intensity distribution. Combining both possibilities, one sensor is placed stationary with respect to the surface and another sensor is placed stationary with respect to the pattern, which is particularly reliable and flexible. In this case, the sensors can also communicate directly with each other, which allows a more reliable and / or accurate determination of the current position.

  Another advantage of determining the current position in a measurement technique is described in detail in a parallel patent application specification filed on the same day by the applicant. According to this, the light amount or light intensity detected by the imaging unit is controlled and changed in relation to the actually determined current position. For example, the brightness of the ambient illumination is changed according to the actual position that is actually determined. The intensity distribution of the filter process can be manipulated by changing the light intensity during the exposure time. In particular, the low-pass filtering in this way makes it possible to generate a sinusoidal intensity distribution from an intensity distribution that is not exactly sinusoidal, which is advantageous for accurate deflection measurement inspection. The relative movement of the pattern can be accurately and synchronously performed according to the actually determined current position.

  Only inconvenient areas of the pattern can be easily and quickly identified based on the current position. An inconvenient area is, for example, an edge where a plurality of portions of the pattern are abutted against each other. In such areas, the butt edge itself or the pattern transition at the butt edge may cause errors in determining the surface properties. A quick and inexpensive detection of inconvenient areas allows simple use of the correction means. Thereby, it is possible to automatically achieve a higher degree of inspection accuracy at a low cost.

  Therefore, the above problem has been completely solved.

  In an advantageous configuration of the invention, the measuring unit has at least one optical sensor.

  In this configuration, the current position is detected optically. This has the advantage that the current position can be located in a non-contact manner without wear. This provides the robustness of the device with respect to inconvenient effects due to aging and measurement accuracy based on temperature fluctuations. The optical sensor may advantageously be a reflective light barrier. Furthermore, it is also possible to use an additional imaging unit or an already provided imaging unit as an optical sensor.

  In another configuration, the measuring unit has at least one marking area fixedly connected to the pattern.

  In this configuration, a marking area is particularly provided, and the current position of the first intensity distribution is detected using this marking area. Based on the fixed relationship between the marking area and the pattern, the current position of the intensity distribution can be determined very easily and quickly using the position of the marking area. A separate marking area always has the advantage that measurements can be taken within a given local area, whereby the optimum conditions for the measurement can be set inside this area. This can be done independently of the conditions for the surface inspection, which advantageously allows the current position to be detected independently of the surface inspection. It is particularly advantageous if the marking area extends in the direction of relative movement between the surface and the first intensity distribution. It is also possible to arrange the marking area within the first intensity distribution or over the first intensity distribution. If the marking area is placed in or in the pattern, it is possible to design the marking area so as not to affect the optical inspection of the surface or only slightly.

  In another configuration, the pattern has an edge region that forms a marking region.

  In this configuration, the pattern itself includes a marking area. The current position is preferably detected in the edge region. This has the advantage that the sensor can be placed in the edge region of the pattern, whereby the surface inspection is not affected or essentially not affected by the measuring unit. The pattern forms a characteristic structure in the direction of relative movement along the edge region. Thereby, the movement of the pattern in the length direction of the edge region can be detected, and consequently, the current position of the first intensity distribution can be detected. If the edge region has a sufficient width in the lateral direction with respect to the relative movement, the lateral movement with respect to the length of the edge region can also be measured.

  In another configuration, the marking area is adjacent to the edge of the pattern.

  In this configuration, the marking area is located outside the pattern. In this case, it is advantageous that the marking area can be configured independently of the pattern implementation. At the same time, the marking area adjacent to the edge of the pattern forms an edge area that is additionally attached to the pattern, thus providing the advantages of the above arrangement. It is also possible to superimpose the marking area and the pattern so that the marking area limits the pattern.

  In another configuration, the auxiliary pattern is arranged in the marking area.

  In this configuration, additional patterns and auxiliary patterns are arranged in the marking area. Thereby, the current position of the first intensity distribution can be easily detected. In this case, it is advantageous that the auxiliary pattern can be made rougher or finer than the pattern as required. Auxiliary patterns containing the actual current position code in the form of absolute values are advantageous. Thereby, not only the change of the current position but also the absolute value of the current position can be directly detected. Alternatively, an incremental pattern that is simpler than the auxiliary pattern is also conceivable, which allows detection of changes in the current position.

  In this configuration, the auxiliary pattern is a rectangular pattern.

  In this configuration, a rectangular pattern is used to detect the current position of the first intensity distribution. In this case, the rectangular pattern can be technically very easily implemented by making a bright area and a dark area continuously or stepwise. Advantageously, the bright area and the dark area are configured with the same length in the extending direction of the marking area, whereby the first intensity distribution is displaced for each detection of a change in intensity of the rectangular pattern. It can be regarded as equivalent to a predetermined distance. A high resolution for detecting the current position is obtained by using a rectangular pattern having a high high frequency. It is also possible to use a number of sensors that are offset from one another along the auxiliary pattern. Thereby, the intermediate value at the time of displacement can advantageously be detected as the current position.

  In another configuration, the support element has a pattern and a marking area.

  In this configuration, the support element has a pattern and a marking area, in which case the pattern and the marking area are fixedly coupled to each other by the support element and do not displace the marking area with respect to the pattern. It is advantageous that it can be arranged in the device easily. In this way, a particularly accurate arrangement of the marking areas with respect to the pattern is obtained. As the support element, for example, a thin film or paper can be considered. However, the configuration of the support element is related to the configuration of the device, and a tunnel wall or eg a plastic plate is also considered as the support element. The pattern and the marking area may be arranged on the support element in different forms. For example, they can be drawn, printed or glued on the support element. It is also possible to project the pattern and the marking area onto the support element. Furthermore, transmissive or reflective surfaces are also conceivable as support elements, these surfaces forming patterns and marking areas by partially changing the optical properties. Such a change can be made, for example, by etching the support element or by partial polishing. It is also particularly advantageous to use exchangeable support elements that can be exchanged in the device as required. Thereby, a pattern can be configured quickly and easily at low cost, and at the same time, the marking area can be held stationary with respect to the pattern. In this way, the accuracy of the measuring unit is increased with a cost advantage.

  In another configuration, the pattern and the marking area are arranged on the tube element, and the marking area extends in the circumferential direction of the tube element.

  In this configuration, the tube element forms a holding device for the pattern and the marking area when the pattern and the marking area are arranged on one support element or forms the support element itself. The displacement of the pattern relative to the surface can be obtained by rotation of the tube element about the longitudinal axis. This presupposes an appropriate selection of patterns. In this way, movement of the tube element about the longitudinal axis can be detected very easily. The use of the tube element has the advantage that the displacement of the first intensity distribution relative to the surface can be performed very simply by rotation of the tube element. This further provides the advantage in the arrangement that a very simple and compact device as a whole is obtained. At the same time, the pattern can be displaced “infinitely” along the surface. At the same time, the current position of the first intensity distribution can always be detected. Particularly advantageously, when a tube element is used in connection with an optical sensor, it is advantageous to position the optical sensors at different angles along the marking area, so that the current position can be detected. Increases resolution. Both the pattern and the marking region may be located on the outer peripheral surface of the tube element or the inner peripheral surface of the tube element. It is also possible to use a translucent tube element, whereby the inner area of the tube element can be illuminated from the outside, or the outer area of the tube element can be illuminated from the inside of the tube element. it can.

  In another configuration, the control unit displaces the first intensity distribution relative to the measurement unit.

  In this configuration, the current position of the first intensity distribution is used to monitor or adjust the displacement of the first intensity distribution. Errors in displacing the first intensity distribution are minimized or completely prevented. At the same time, continuous and constant movement is guaranteed. In a preferred embodiment, the measurement unit and the control unit form a movement adjuster for the displacement of the first intensity distribution.

  In another configuration, the imaging unit captures an image in association with the measurement unit.

  In this configuration, the imaging unit is controlled in relation to the current position of the first intensity distribution determined by the measurement technique. In this case, the starting time, i.e. the time of starting the shooting, can also be advantageously controlled in relation to the current position. The end point, i.e. the point at which imaging ends, can also advantageously be controlled in relation to the current position. Alternatively, only the starting time can be triggered relative to the current position, and the exposure time is set constant. Control related to the position of at least one of the two parameters allows the imaging to be adapted to the intensity distribution very accurately. A predetermined area of the pattern can be intentionally omitted. Furthermore, the imaging unit can be started accurately, ie synchronously, when the desired current position of the pattern is provided. As a result, it is possible to prevent an erroneous current position from being generated at the time of imaging and causing a wavy defect in each image. By controlling the exposure time, that is, by opening and closing the shutter of the imaging unit, it is possible to detect the movement of the first intensity distribution over a predetermined time. Thereby, an intermediate value about the intensity of the intensity distribution with time is partially generated in the image. In other words, the intensity distribution is “clogged” over a longer exposure time. This action makes it possible to generate a continuous flexible pattern in the image. In this way, for example, a flexible and continuous pattern corresponding to a pattern actually produced and scanned by the dithering printing method is generated in the image. This eliminates, in particular, printing technology obstacles completely or at least extensively.

  In another configuration, the evaluation unit determines surface characteristics in relation to the measurement unit.

  In this configuration, the current position of the first intensity distribution is used to evaluate the image. In this case, it is advantageous to be able to detect whether the first intensity distribution has been displaced inadvertently or not at all. Predetermined areas of the pattern can also be identified, which gives rise to the possibility of adapting and evaluating the resulting image associated with this area of the pattern or not at all.

  It will be appreciated that the features described above and further described below can be used not only in the respective combinations described above, but also in other combinations or alone without departing from the scope of the claims of the present invention.

  Embodiments of the invention are illustrated and described in detail below.

  An apparatus and method for optically inspecting the surface of an object according to the present invention provides an alternative apparatus and method for inspecting a surface extensively automatically, quickly, reliably and with high accuracy. The resulting apparatus and method according to the present invention can be used universally and can be implemented at low cost.

FIG. 2 is a schematic side view of an embodiment of the apparatus of the present invention for optically inspecting the surface of an object with a measuring unit. It is a top view of the apparatus shown in FIG. It is a side view at the time of the optical inspection of the surface in the apparatus shown in FIG. FIG. 4 is a schematic diagram of another embodiment of the apparatus of the present invention. It is a fragmentary figure which shows the Example of the support element which has a pattern. FIG. 6 is a partial view showing another embodiment of a support element having a pattern.

  1, 2, 3, and 4, an apparatus of the present invention is shown, generally designated by the reference numeral 10.

  FIG. 1 shows a side view of the device 10. The apparatus 10 has a base plate 12, and holding parts 14 and 16 are arranged on the base plate 12. The holding unit 16 has a driving unit and is connected to the control unit 20 by a line 18. FIG. 1 shows a partially sectioned side view, so that only the side views of the holding parts 14 and 16 are shown. The holding parts 14 and 16 support a tube element 22 having a longitudinal axis 24. The longitudinal axis 24 is oriented parallel to the base plate 12. The holding portions 14 and 16 support the tube element 22 on the outer peripheral surface. This support is here implemented in such a way that the tube element 22 can rotate about the longitudinal axis 24. In this case, the thin film 26 is disposed on the inner peripheral surface of the tube element 22. The thin film 26 serves as a carrier for the pattern 28. The pattern 28 has a dark area 29 and a bright area 30. These continuous regions 29 and 30 form two periodic intensity distributions 31 and 32 each having a predetermined period extending in the lateral direction. In one embodiment, the bright area 29 and the dark area 30 form a pattern having rectangular intensity distributions 31 and 32. Here, the regions 29 and 30 are dramatically shifted from each other at a periodic location 33. In other embodiments, the intensity distribution may be formed with other transitions that are sinusoidal, serrated, or continuous. The illustrated pattern 28 is caused by two stripe groups that intersect perpendicularly to each other. The first and second intensity distributions 31 and 32 for the pattern 28 are generated orthogonal to the direction of the stripe group. The stripe groups may have different stripe widths. The pattern 28 here ends with an edge 34 that extends along the inner peripheral surface of the tube element 22 in the circumferential direction about the longitudinal axis 24. At the edges 34, one marking area 35 is adjacent to the stripe 28. In other embodiments, individual marking areas 35 may be provided at the edge 34.

  The marking area 35 is shown without detailed marking in FIGS. 1-4 for clarity. The marking area 35 is in this case attached to the membrane 26 together with the pattern 28. As a result, the pattern 28 and the marking region are in a firm (fixed) spatial relationship with each other. The marking area 35 here cooperates with an optical sensor 38. Here, one marking area 35 includes two optical sensors 38, and another marking area 35 includes one optical sensor 38. The optical sensor 38 is connected to the evaluation unit 46 by lines 40, 42 and 44. The evaluation unit 46 evaluates the information supplied by the sensor 38 and thereby determines the current position of the intensity distributions 31, 32. The sensor 38 here forms a measuring unit 48 with the marking area 35, by means of which the current position of the intensity distributions 31, 32 can be determined. In order to optically inspect the surface of the object, the imaging unit (camera) 50 is arranged to look at the internal space of the tube element. The camera 50 is connected to the evaluation unit 46 by a line 52. Evaluation unit 46 evaluates the image of camera 50 to inspect the surface.

  Furthermore, the device 10 has a receiving part 54 in which an object 56 having a surface 58 to be inspected is arranged. A light source 62 is attached below the housing portion 54, and the light source 62 plays a role of providing sufficient light intensity during optical inspection. Furthermore, an alternative or additional light source 62 ′ is shown above the tube element 22. This light source 62 ′, together with the translucent material of the tube element 22, provides sufficient illumination inside the tube element 22. The accommodating part 54 can be moved in the direction of the arrow 64, thereby moving the object into the tube element 22.

  FIG. 2 shows a top view of the apparatus 10 of FIG. The tube element 22 is shown further broken away. In order to better show the holding parts 14 and 16, the pattern 28 is only partially shown. The holding portion 16 has a driving roller 66 that contacts the outer peripheral surface of the tube element 22 and rotates the tube element 22. The holding element 14 has a support roller 68 that supports the tube element 22 on the outer peripheral surface. The driving roller 66 is rotatably supported by the holding portion 16 and the support roller 62 is rotatably supported by the holding portion 14. Camera 50 and line 52 are shown as dotted lines for ease of viewing.

  FIG. 3 shows a side view during optical inspection of the surface 58 of the object 56 in the apparatus 10 shown in FIGS. For optical inspection, the receptacle 48 was moved into the tube element 22 along with the object 56 in the direction of arrow 64. During inspection of the surface 58, the tube element 22 rotates about the longitudinal axis 24, thereby moving the membrane 26. Based on the configuration of the pattern 28, the first intensity distribution 34 and the second intensity distribution 36 are displaced with respect to the surface 52 by rotation.

  The control unit 20 controls the driving device of the holding unit 16 so that the tube element 22 rotates about the longitudinal axis 24. In order to be able to inspect the surface 58 with sufficient illumination, the light source 62 is switched on to produce a light cone 70. Alternatively or additionally, the light source 62 'can be used to obtain sufficient illumination. In this case, it is advantageous if the tube element 22 is made from a translucent material.

  In order to inspect the surface 58, a plurality of images are taken one after another by the imaging unit 50. In this case, the intensity distributions 31 and 32 are located at different positions with respect to the surface 58. Preferably, each inspection surface location is imaged at least 4 times, and the surface location has a different relative position to the intensity distributions 31, 32 in each of at least 4 images. Furthermore, it is advantageous if at least four images cover exactly one period of the intensity distribution. In this case, for example, as described in Patent Document 1 mentioned at the beginning, an image can be evaluated very simply by a known “4-bucket method” as a deflection measurement method.

  The inspection of the surface 58 is performed inside the imaging region 70 where the surface 58 to be inspected is detected. A surface that cannot be completely detected within the imaging region 70 can be inspected piece by piece by displacing the object along the longitudinal axis 24. The image taken by the camera 50 is transmitted to the evaluation unit 46 for evaluation.

  The rotational movement of the tube element 22 is detected by the measuring unit 48 and likewise transmitted to the evaluation unit 46. Based on the measurement values supplied by the measurement unit 48, it can be determined whether and how much the pattern and thus the intensity distributions 31, 32 has been displaced relative to the surface 58. Further, it can be determined whether an area of the pattern 28, for example, the butt edge 36 has been detected by the camera 50. In one embodiment, the evaluation unit 46 controls the movement of the tube element 22 by the control unit 20 based on the current position determined by the measurement unit. Furthermore, in this preferred embodiment, the evaluation unit 46 starts the camera 50 in relation to the current position of the tube element 22 and thus in relation to the current position of the intensity distributions 31, 32, so that it is based on the current position. Then, the time of shooting by the camera 50 is determined.

  FIG. 4 shows another embodiment of the device 10. The embodiment of FIG. 4 differs from the embodiment of FIG. 1 by using a conveyor belt as the accommodating portion 54. In this case, the light source 62 is fixed to the conveyance belt in a stationary manner with respect to the base plate 12. As a result, the light source 62 always takes the same spatial position inside the rotating tube element 22, thereby obtaining a constant illumination. By using a conveyor belt as the accommodating portion 54, there is an advantage that a large number of objects 56 can be inspected quickly and one after another. Furthermore, this embodiment allows a very simple integration of the device 10 into an existing production line.

  FIG. 5 shows an example of a portion of the thin film 26. The pattern 28 extends to the marking area 35, so that the edge area 78 of the pattern 28 forms the marking area 25. This embodiment provides the advantage that the pattern 28 may extend over the entire inner surface of the tube element. The current positions of the intensity distributions 31, 32 can here be detected in the edge region 78 on the basis of periodic alternating light-dark.

  FIG. 6 shows another embodiment of the thin film 26. In this embodiment, the pattern 28 is located in the center of the thin film 26 and has two edges 34. Adjacent to the edge 34 are each here another rectangular pattern 84. The rectangular pattern 84 forms the marking area 35. The marking area 35 extends in a plane perpendicular to the longitudinal axis 24 of the tube element, here substantially over the entire inner circumference of the tube element 22. In this embodiment, it is advantageous that a unique pattern different from the pattern 28, that is, an auxiliary pattern is provided in the marking area 35. In a particularly advantageous embodiment, the auxiliary pattern forms an incremental sensor with the optical sensor 38, which makes it very easy to track the rotational movement of the tube element 22 about the longitudinal axis 24. . However, in principle, the auxiliary pattern may represent the absolute position of the tube element relative to a predetermined start position. The auxiliary pattern may be substantially simpler than the pattern 28. Advantageously, the auxiliary pattern is implemented as a rectangular pattern having a period shorter than the period of the intensity distribution. As the period becomes shorter, the current position is determined more finely. Unlike the embodiment shown, the device may be constituted by only one marking area 35. Further, in principle, the pattern 28 may have only one intensity distribution 31, or may have two or more intensity distributions 31 and 32.

  In another embodiment of the present invention, as is known from US Pat. In this case, it is advantageous if the sensor 38 is arranged in a stationary position (stationary) with respect to the surface 58 and is displaced relative to the pattern 28 together with the surface.

DESCRIPTION OF SYMBOLS 10 Apparatus 20 Control unit 26 Support element 28 Pattern 29,30 area | region 31 Intensity distribution 35 Marking area 38 Sensor 46 Evaluation unit 48 Measurement unit 50 Imaging unit 56 Object 58 Surface

Claims (14)

In an apparatus (10) for optically inspecting a surface (58) of an object (56),
A pattern (28) having a number of bright and dark areas (29, 30) forming a spatial first intensity distribution (31) having a spatial first period;
A receiving portion (54) for positioning the object (56) having the surface (58) relative to the pattern (28) so that the first intensity distribution (31) corresponds to the surface (58). When,
The first intensity distribution (31) is displaced by a predetermined displacement distance relative to the surface (58), and the surface (58) moves relative to the first intensity distribution (31) along the displacement distance. A control unit (20) for taking a number of different relative positions;
At least one imaging unit (50) for taking a number of images showing the surface (58) at different positions together with the first intensity distribution (31);
An apparatus having an evaluation unit (46) for determining a characteristic of said surface (58) in relation to an image,
Apparatus comprising a measurement unit (48) configured to detect a current position of the first intensity distribution (31) relative to the object (56). Device (10) according to claim 1,
Apparatus wherein the measurement unit (48) comprises at least one optical sensor (38). The apparatus according to claim 1 or 2,
Apparatus wherein the measurement unit (48) has at least one marking area (35) fixedly coupled to the pattern (28). Device (10) according to claim 3,
Apparatus wherein the pattern (28) has an edge region (78) that forms the marking region (35). Device (10) according to claim 3 or 4,
Apparatus wherein the marking area (35) is adjacent to an edge (82) of the pattern (28). The device according to any one of claims 3 to 5,
A device in which an auxiliary pattern (84) is arranged in the marking area (35). The apparatus of claim 6.
The device wherein the auxiliary pattern (84) is a rectangular pattern (84). In the device (10) according to any one of claims 3 to 7,
A device in which a support element (26) comprises the pattern (28) and the marking area (35). Device (10) according to any one of claims 3 to 8,
The device wherein the pattern (28) and the marking area (35) are arranged in a tube element (22), and the marking area (35) extends in the circumferential direction of the tube element (22). Device (10) according to any one of claims 1 to 9,
Apparatus wherein the control unit (20) displaces the first intensity distribution (31) relative to the measurement unit (48). Device (10) according to any one of claims 1 to 10,
An apparatus in which the imaging unit (50) captures an image in relation to the measurement unit (48). Device (10) according to any one of the preceding claims,
Apparatus in which the evaluation unit (46) determines the characteristics of the surface (58) in relation to the measurement unit (48). A method for optically inspecting a surface (58) of an object (56) comprising:
Providing a pattern (28) having a number of bright and dark areas (29, 30) forming a spatial first intensity distribution (31) having a spatial first period;
Positioning the object (56) having a surface (58) relative to the pattern (28) such that the first intensity distribution (31) is on the surface (58);
The first intensity distribution (31) is displaced by a predetermined displacement distance relative to the surface (58), and the surface (58) moves relative to the first intensity distribution (31) along the displacement distance. Taking a number of different relative positions,
Taking a number of images showing the surface (58) at different positions with the first intensity distribution (31);
Determining a characteristic of said surface (58) in relation to an image,
A method of determining a current position of the first intensity distribution (31) relative to the object (56).   14. All the steps of the method according to claim 13 when programmed on a computer of the device according to any one of claims 1 to 12, comprising program code and stored on a data carrier. A computer program characterized by being implemented.

Images